The Art of Computation, Designed to Teach Practical Methods of Reckoning, with Accuracy and Rapidity

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D. W. Goodrich, 1873 - Ready-reckoners - 206 pages
 

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Page 50 - ... the square of the second. _ Again, (a — by = (a — 5) (a — 5) = a2 — 2a6 + 52. (2) That is, The square of the difference of two quantities is equal to the square of the first, minus twice the product of the first by the second, plus the square of the second.
Page 141 - WORK. BRICKWORK is estimated at the rate of a brick and a half thick. So that if a wall be more or less than this standard thickness, it must be reduced to it, as follows : Multiply the superficial content of the wall by the number of half bricks in the thickness, and divide the product by 3. The...
Page 75 - Multiply each numerator into all the denominators except its own for a new numerator, and all the denominators together for a common denominator.
Page 192 - ... and directed that the remainder be given in farms of precisely the same shape and size to his four sons. Required the shape and size of each ? 9. Supposing there are more persons in the world than any one of them has hairs on his head, it then follows as a necessary consequence, that some two of them at least, must have exactly the same number of hairs on their heads, to a hair : required the proof.
Page 171 - These are usually accounted six in number, viz. the Lever, the Wheel and Axle, the Pulley, the Inclined Plane, the Wedge, and the Screw.
Page 133 - Multiply the amount of the smaller side by the number of days between the two average dates, and divide the product by the balance of the account. The quotient will be the time...
Page 175 - A afterwards took 60 alone, which he sold as before at 5 for $2, and received but $24 : what became of the other dollar ? This is rather a catch question, the insinuation that the first lot were sold at the rate of 5 for $2, being only true in part. They commence selling at that rate, but after making ten sales, A's pigs are exhausted, and they have received $20 ; B still has 10 which he sells at
Page 18 - The greatest common divisor of two or more numbers, is the greatest number which will divide them without a remainder. Thus 6 is the greatest common divisor of 12, 18, 24, and 30.
Page 129 - Multiply each payment by its term of credit, and divide the sum of the products by the sum of the payments ; the quotient will be the average term of credit.
Page 185 - ... water side a boat which can carry but two persons at once, and for want of a waterman, they are necessitated to row themselves over the river at several times : The question is, how those...

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